Various processes for the preparation of nucleosides are known per se. For example, Y. Furukawa et al in Chem. Pharm. Bull. 16:1067 (1968) described the reaction of purines with 1-O-acyl or 1-O-alkyl derivatives of a sugar in the presence of Friedel-Crafts catalysts to obtain the corresponding N-glycosides. German Pat. No. 1,919,307 discloses a process for the production of nucleosides in which silylated N-heterocyclic bases are reacted with masked 1-halo-, 1-O-alkyl-, and especially 1-acyl-sugars in the presence of Friedel-Crafts catalysts. Technical scale application of such conventional processes can be complicated because the separation of the salts of the Lewis acids and/or Friedel-Crafts catalysts formed during the reaction frequently causes difficulties in working-up the reaction mixtures and additional chemical operations thus become necessary. These disadvantages also manifest themselves in a reduced yield of the finally desired product.